【作者】 盛湘飞；

【导师】 夏琴香；

【作者基本信息】 华南理工大学 ， 机械制造及其自动化， 2014， 博士

【摘要】 飞机结构件都在受载及各类腐蚀环境下工作，常出现腐蚀疲劳和应力腐蚀等腐蚀损伤。随着服役时间的增加，现有波音、空客等民用飞机老龄化趋势不断加剧（老龄飞机面对的主要问题是疲劳、腐蚀和磨损）。大量存在的腐蚀损伤，是民用飞机结构修理不可忽视的内容。本文在国家自然科学基金委员会与中国民用航空局联合资助项目“基于民用飞机结构件腐蚀损伤条件下喷丸强化机理的研究”（课题编号：61179051）的资助下，以腐蚀损伤飞机结构件为研究对象，综合采用理论分析与试验相结合的方法，深入研究了腐蚀损伤条件下飞机结构件的喷丸强化机理。针对多弹丸随机有限元模型存在运算量过大的问题，首次提出了基于历史信息自动传递的模型简化方法、基于移动矢量的随机弹丸模型的快速建模方法和稳态残余应力的求解方案，解决了随机弹丸模型建模难的一系列关键问题；提出了表面覆盖率的计算方法，实现了定量分析表面覆盖率对残余应力场分布规律的影响；采用Python语言开发了面向Abaqus的随机弹丸几何模型生成、多Job文件自动提交和基于移动矢量快速建模的子程序；建立了基于Abaqus的喷丸强化非线性有限元数值模型；对比分析了不同摩擦系数μ和沙漏刚度系数对有限元模拟结果的影响。获得的研究成果为后文喷丸强化机理研究提供了可靠保障。对铝合金飞机结构件的腐蚀损伤机制、类型及腐蚀损伤区域的形貌进行了归纳和总结，并对其腐蚀损伤打磨区域的几何特征进行了分类；在此基础上，基于随机弹丸喷丸强化有限元模型，采用固定喷射角度喷丸强化方法，对在一定喷丸强化工艺参数条件下的不同几何特征（包括不同表面形状和不同圆角半径rd）的残余应力场分布进行了研究。揭示出不同几何特征的残余应力场分布规律是“表面残余应力σ_srs和最大残余压应力σmcrs由大到小的排列顺序为：凹圆弧面、凸凹面、双凹面、平面、凸圆弧面、双凸面。对于凸圆弧面，rd越大， σ_srs和σ_mcrs越大；而对于凹圆弧面，rd越大，σ_sr和σ_mcrs越小。σ_mcrs对应层深z_m和残余压应力层总深度z₀变化不明显”。基于应力局部坐标转换方法，对结构件过渡区域内不同几何特征在相同喷丸强化工艺参数和不同喷丸强化方法条件下的残余应力场分布规律进行了深入分析；基于Herz接触理论，获得了不同喷丸强化工艺参数条件下喷丸强度AH_sat的解析法计算模型；计算得到了结构件达到100%表面覆盖率所需的弹丸数；同时以凹圆弧面几何特征为例，对凹圆弧面在多种不同喷丸强化工艺参数条件下的残余应力场分布进行了探究；以两侧开口型的打磨区域为例，分别就喷丸残余应力场、表面组织结构和形貌特征变化对喷丸强化效果的影响进行了深入研究。得到的结论具有较高的理论和工程应用价值，为喷丸强化工艺在腐蚀损伤飞机结构件修复中的实际应用奠定了良好的基础。本文从试验角度基于新的试验方案研究了不同喷射压力Ps和弹丸直径Ds组合下的喷丸强度AHsat；基于数字图像处理法计算得到了不同Ps和Ds条件下达到100%表面覆盖率所需的喷丸循环次数，并结合正态分布对相邻两喷丸强化道次之间的距离进行了优化；对喷丸强化后结构件的表面粗糙度特征值Ra和表面残余应力σ_srs进行了测量和分析；研究了喷丸强化后结构件的疲劳性能；并将AH_sat、R_a、σ_srs和疲劳试验的试验分析结果与理论分析结果进行对比，发现两者吻合较好，即表明本文的理论分析结果的准确性和可靠性。更多还原

【Abstract】 Aircraft structural parts have been working under the condition of load and all kinds ofcorrosive environments, some corrosion damage phenomenons will occur frequently, such ascorrosion fatigue and stress corrosion etc. Aging trend of existing civil aircraft such as Boeing,Airbus ect is growing with the increase of service time (fatigue, corrosion and wear are themain problems of the aging aricraft to face). A large number of existing corrosion damagescan not be ignored in the repair process of civil aircraft structural parts.The research of this thesis was financially corporately supported by National NaturalScience Foundation of China and Civil Aviation Administration of China (Subject title:Research on Shot peening Strengthening Mechanism of Civil Aircraft Structures withCorrosion Damage; Subject No.:61179051), civil aircraft structural parts with corrosiondamage were selected as the object of study, a integrated method of combining theoreticalanalysis and experimental study was employed, shot peening strengthening mechanism ofcivil aircraft structural parts with corrosion damage were studied deeply.For the excessive computation problem of multi-shots random finite element model,model simplified method based on automatic transmitting of the historical information, rapidmodeling method based on movement vector, solving scheme of stabilized residual stresswere put forward, a series of key issues were worked out; Calculation method of surfacecoverage was put forward, which implemented the quantitative analysis of influence ofsurface coverage on distribution rule of residual stress; Some subprograms abaqus-orientedwere developed by employing Python language for estalishing random-shots geometricalmodel, autocommitting job files and rapid modelling based on movement vector; Nonlinearfinite element numerical models for shot peening were established based on Abaqus; And theinfluence of different friction coefficient μ and the hourglass stiffness coefficient on theresults of finite element simulation were analyzed. The research results guarantee theaccomplishment of the study about shot peening strengthening mechanism.Mechanism and type of corrosion damage and the topography of corrosion damage areaswere concluded and summarized for aluminum alloy aircraft structural parts (AAASP),geometrical features located in grinding area of AAASP were classified; Residual stress fielddistribution for different geometrical features (including different shape of surface and filletradius rd) were studied by employing shot peening method with fixed angle based onrandom-shots shot peening FEM. Residual stress field distribution rule for differentgeometrical features were revealed "the order from big to small of surface residual compressive stress srsand the max residual compressive stress mcrsis concave arc surface,convex-concave surface, bi-concave surface, flat surface, convex arc surface, bi-convexsurface. For convex arc surface, and increase with the increment of fillet radiusrd; For concave arc surface, and decrease with the increment of fillet radius rd.the variation of the corresponding depthz mwith and the total depthz0of residualcompressive stress are not obvious ".Residual stress field distribution rule for different geometrical features located intransition region of structural parts were analyzed deeply, with the identical shot peeningstrengthening process parameters and different shot peening strengthening method, based onlocal coordinate transformation method of stress; A analytic calculating model of Almenintensity AHsatwith different shot peening strengthening process parameters was obtained;The required number of shots for achieving100%surface coverage of structural parts werecalculated; Taking concave arc surface for example, residual stress field distribution of whichwas discussed with different shot peening strengthening process parameters; And takinggrinding area of two sides with open mouth for example, the influence of residual stress field,organization structure and surface topography characteristics for structural parts after shotpeening strengthening on effect of shot peening strengthening were analyzed in detail. Theresults have higher theory and engineering application value, which establish a soundfoundation for the practical application of shot peening strengthening process in aircraftstructural parts repair with corrosion damage.Almen intensity AHsatfor different injection pressure Psand shot diameter Dswerestudied based on novel experiment scheme; Required cycle number of shot peening forachieving100%surface coverage were obtained with different Psand Dsbased on digitalimage processing method, the distance between adjacent two passes of shot peeningstrengthening was optimized combined with normal distribution; Surface roughness Raandsurface residual stress of structural parts were measured and analyzed; The fatigueperformances of structural parts after shot peening strengthening were studied. And theexperimental results of AHsat, Ra, and fatigue test were used to compare with thetheoretical analytical results in chapter3and4. which show that the theoretical analyticalresults are accurate and reliable.更多还原